1. Field of the Invention
The present invention relates to an on board indicator for vehicles, for controlling the slow variations of a physical magnitude affected by rapid parasite variations, including a sensor for sensing said physical magnitude, including an electric signal output corresponding to the physical magnitude, means connected to said sensor for displaying said output magnitude and means for damping the parasite variations of the indication thus obtained of said physical magnitude.
Such an indicator is used, for example, for indicating the level of fuel in the reservoir of any vehicle, particularly a motor vehicle.
In such a case, it is important to be able to check the mean level in the reservoir, whose variations are slow with respect to the rapid parasite variations caused by the movements of the vehicle.
2. Description of the Prior Art
Such on board indicators are already known, in which the display means include a needle apparatus of the galvanometer type with moving coil, and the damping means includes a device for mechanically damping the moving coil, using, for example, viscous friction. Since the damping thus obtained is sometimes insufficient, and when the sensor includes a movable mechanical member, such for example as a float in the case where the magnitude to be indicated is a level, another device is provided for damping this movable member mechanically by viscous friction or inertia. These devices have the following drawback. In order to obtain sufficient damping of the parasite variations when the vehicle is running normally, they must be adjusted in a way such that the result is a false indication in the time period immediately following switching on of the ignition of the vehicle. In fact, the mobile frame cannot move rapidly for the needle to overcome almost instantaneously the discontinuity corresponding to switching on of the ignition of the vehicle. In addition, viscous or inertia damping devices are relatively expensive.
The present invention aims at overcoming the above drawbacks.